1. Field of the Invention
The present invention relates to sound source apparatuses capable of generating a musical tone based on note data (musical tone data) received from an external device, and, more particularly, to sound source apparatuses which, when a plurality of sound source apparatuses are mutually connected, can cooperatively function as a single sound source apparatus.
2. Description of the Related Art
Due to appearance of a MIDI (Musical Instrument Digital Interface) system and development of an electronic musical instrument employing a digital signal processing, it is possible to mutually connect a plurality of electronic musical instruments via a MIDI and play a music synchronizing them. Particularly, many electronic musical instruments of sound source module type excluding a music-playing section such as a keyboard, have been developed for the purpose of such a synchronous performance. With a plurality of sound source modules of this type mutually connected, a high performance effect can be attained.
The above sound source module is connected with an external keyboard or the like and receives MIDI data such as NOTE ON data (tone generation instruction data) or NOTE OFF data (note off instruction data) therefrom to thereby perform tone generation control such as generation of a musical tone (note on) or note off. In this case, a single sound source module can normally generate a plurality of musical tones in parallel through time-divisional processing and typically has about 8 to 16 polyphonic channels. With a plurality of such sound source modules being mutually connected via a MIDI, these modules can perform synchronous musical performance when independently receiving MIDI data. In this case, sound source modules each having 8 to 16 polyphonic channels perform tone generation independently and in parallel.
According to the above prior art, however, a plurality of sound source modules simply execute a musical performance in parallel. Functions of these sound source modules cannot be expanded, nor can they be used as a single sound source module. This problem may be overcome by permitting expansion of a sound source by specifying a tone region in use for each sound source module and determining the presence or absence of a musical tone being generated according to a note No. (number specifying a pitch) entered externally. In this type, a sound source module which generates a musical tone is determined by the tone region of a musical performance, so that using a certain tone region many times, the number of polyphonic tones involved may exceed the number of polyphonic tones allowed per sound source module. This makes further tone generation impossible in spite of remaining polyphonic channels to be able to generate tones, and narrows or limits the range of flexibility or freedom of a musical performance.